Effect of pressure and temperature on viscosity of a borosilicate glass

During industrial glass production processes, the actual distribution of stress components in the glass during scribing remains, to date, poorly quantified, and thus continues to be challenging to model numerically. In this work, we experimentally quantified the effect of pressure and temperature on the viscosity of SCHOTT N-BK7((R)) glass, by performing insitu deformation experiments at temperatures between 550 and 595 degrees C and confining pressures between 100 and 300MPa. Experiments were performed at constant displacement rates to produce almost constant strain rates between 9.70x10(-6) and 4.98x10(-5)s(-1). The resulting net axial stresses range from 81 to 802MPa, and the finite strains range from 1.4% to 8.9%. The mechanical results show that the SCHOTT N-BK7((R)) glass is viscoelastic near the glass transition temperature at 300MPa of confining pressure. To elucidate the data, we incorporated both 1-element and 2-element generalized Maxwell viscoelastic models in an inversion approach, for which we provide MATLAB scrips. Results show that the 2-element Maxwell model fits the experimental data well. The stress decreases with increasing temperature at 300MPa and the temperature dependence yields a similar activation energy (601 +/- 10kJmol(-1) or H/R=7.2x10(4)K) to a previously reported value at 1-atm (615kJmol(-1) or H/R=7.4x10(4) K). The SCHOTT N-BK7((R)) glass shows a limited linear increase in viscosity with increasing pressure of similar to 0.1log(10)(Pas)/100MPa, which is in agreement with the most recent 2-internal-parameter relaxation model (based on experiments).